E. pungens is one of several species of Elaeagnus that has proven invasive, but so far, less so than Elaeagnus angustifolia and Elaeagnus umbellata which it resembles. This dense evergreen and often ...
E. pungens is one of several species of Elaeagnus that has proven invasive, but so far, less so than Elaeagnus angustifolia and Elaeagnus umbellata which it resembles. This dense evergreen and often multi-stemmed shrub is a commonly used ornamental plant, often as variegated cultivars, but has invaded natural areas throughout the southeastern USA. It is very tolerant of wind, salt and shade, but will invade both in open areas and in forests. The fruit is widely consumed by animals and can spread rapidly.
Elaeagnus is placed in its own family, the Elaeagnaceae, also containing the genera Hippophae and Shepherdia. There are about 80 species within the genus with a wide distribution in eastern Asia (Zheng et al., 2006). Elaeagnus pungens is placed in section Sempervirentes (Tzvelev, 2002). Being a respected ornamental species, there are a number of cultivars including probably the most widespread, cv. Maculata, but also Aurea, Dicksonii, Frederici, Fruitlandii, Gold Rim and Variegata amongst others. These are sometimes given higher ranks such as form or variety, and subspecies have also been proposed. For the purposes of this datasheet, a single undivided species is accepted with numerous cultivars. It is most commonly known as the thorny olive or silverberry.
E. pungens is an evergreen densely branched shrub commonly 3-4 m, but it can be as small as 1 m, and occasionally up to 8 m tall. Spines are frequent on the stems. Young branches densely brown scaly, pubescent when young. Leaves thick and leathery, silver-brown, alternate, oval, elliptical or oblong, 5-10 cm long and 1.8-3.5 (-5) cm wide, with dense whitish scales also often brown, glabrous and glossy above, scaly underneath, lateral veins 7-9 each side of midrib, base rounded, irregular undulate margins, apex obtuse to bluntly acute. Petioles robust, 4-5 (-15) mm long. Flowers fragrant, silvery-white to brown, tubular and 1 cm long, few (1-3), in axillary clusters, pedicel 5-8 mm and scaly brown, calyx tube 6-7 mm long and abruptly narrowed at base, lobes ovate, apex rounded. Fruit oblong, 1.0-1.5 cm, brown scaly containing one nut, white changing to red with spotted brown scales when ripe (adapted from Miller, 2003; Flora of China Editorial Committee, 2008).
E. pungens is native to China and Japan. It has been introduced to the eastern and southeastern USA were it is widely reported, is noted in New Zealand, and also in some European countries with unconfirmed reports from others. Noting its ornamental value and tolerance to drought and saline conditions, it is likely to be present in many more countries than is indicated, especially in northern Europe, but also around the Mediterranean, western USA, Canada, and elsewhere.
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
E. pungenswas first introduced into the USA in 1830 as an ornamental, and it was thought to have been introduced into Europe between 1829 and 1866, first to the Netherlands, by the Bavarian physician Philipp von Siebold who introduced numerous garden plants from Japan into Europe (Christenhusz and Uffelen, 2001). It was also introduced to New Zealand, and to Israel (Hagiladi et al., 1989), though exact dates are not known.
E. pungens is on the Florida and South-East Exotic Plant Pest Council list of invasive plants (USDA-NRCS, 2008), and is also on exotic pest lists for several other states including Alabama, Georgia, South Carolina, Tennessee and Virginia. As a highly valued ornamental it is highly likely to continue to be introduced as any number of the existing or future selected cultivars.
In its native range, E. pungens is often found on open slopes, roadsides or thickets, often near the sea and generally below 1000 m (Flora of China Editorial Committee, 2008). Where introduced and invasive it is also found in scrub and shrublands, and natural forests.
A number of cultivars have been selected and propagated, mostly for variegated foliage. Of these, cv. Maculata and cv. Dicksonii are slower growing variegated forms that also produce good fruit crops, cv. Frederici has especially large fruit 25 mm long, and there are other cultivars including Aurea, Clemson Variegated, Fruitlandii, Gold Rim, Hoksuba Fukurin, Tricolor and Variegata. Frederici is an old cultivar and may have been the original sent to the Netherlands by von Siebold in the mid 1800s (Houtman, 2004). The cultivated hybrid Elaeagnus x ebbingei arose from a cross between E. macrophylla, and pollen from E. pungens and was distributed in 1938 through M Koster and Sons of Boskoop, the Netherlands (Houtman, 2004). Chromosome numbers are not reported.
The scented flowers are hermaphrodite and are pollinated by bees.
Physiology and Phenology
Although commonly described as an evergreen, it may be deciduous in some circumstances. In its native range in China it flowers in September-December and fruits in April-June (Flora of China Editorial Committee, 2008). Where invasive in the USA it flowers in November-February and fruits in April-May. It is a nitrogen-fixing species, via an association with actinomycete fungi. After germination it produces dense multiple stems, with short shoots and small leaves that become branched or unbranched thorns 1-4 cm long. In the second year, lateral branches are produced that are followed by flowers in the autumn (Miller, 2003). It is extremely wind resistant and salt resistant (Houtman, 2004).
It is a nitrogen-fixing species, in association with actinomycete fungi, Frankia spp. (Dommergues et al., 1999), that also nodulate Hippophae and Shepherdia, but not by strains that colonize other actinorhizal plants such as Casuarina and Alnus. Inocula is available for Elaeagnus species, although inoculation may not be necessary since most plants spontaneously nodulate in the nursery or upon planting in the field, and unlike Rhizobium, Frankia survive in the soil for long periods without the presence of host plants. Specific E. pungens strains were identified by Fukumoto et al. (1995).
E. pungensis a species of warm temperate climates, and drought tolerant but can grow in most soils. It prefers a variety of soil types but prefers well-drained soils, and can tolerate infertile and very heavy soils, acid and alkaline conditions, and exposure to salt winds.
There are few records of pests and diseases specifically attacking E. pungens, though further investigation into horticultural diseases affecting ornamental plants would yield additional results. Colletotrichum gloeosporioides [Glomerella cingulata] was first identified as the causal agent of anthracnose in Argentina by Carmona and Wright (1999), and E. pungens was first identified as a new host record for Fusarium solani by Miller (1997).
Zheng et al. (2006) report that 10 fungi have been found on members of the genus Elaeagnus, including Aecidium elaeagni which may be host-specific to Elaeagnus spp. and Septobasidium albidum which has a host range that includes E. umbellata as well as species in other genera. Also, 22 arthropods belonging to 10 families of five orders are reported, and the moth, Teia prisca may be specific to E. angustifolia. All natural enemies are listed along with whether they are known to attack the three main invasive Elaeagnus spp., E. angustifolia, E. pungens and E. umbellata.
As a valued and widely commercialised ornamental species, it has a clear positive economic impact as a traded product in the horticultural industry, though no data is available. However, native alternatives are available in all countries where it is introduced and currently sold.
E. pungens invades natural environments and suppresses native vegetation. There are also unconfirmed reports of it being able to develop a climbing habit, and that it can climb to the tops of trees in northern Italy.
The only social impacts are positive, from the aesthetic value as an ornamental species, and especially in coastal gardens in northern Europe where few other variegated plants can tolerate the harsh conditions.
E. pungens is mainly used for ornamental purposes, and is still a valued ornamental plant in the south-eastern USA from Maryland to Florida, where it is often used in parking lots and in highway medians. In northern Europe, its extreme wind resistant and salt resistant makes it one of the most preferred plants for coastal areas, especially the variegated cultivars (Houtman, 2004).
It has also been planted as a cover for wildlife (Miller and Miller, 1999), and it can be grown as a hedge in exposed positions especially in coastal areas. The fruit, the size of a large blackcurrant, can be consumed raw or cooked though it does contain a large seed, but it has a pleasant sub-acid flavour when fully ripe, and can be made into jams and drinks.
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
There are few reports of specific control methods for E. pungens, however, it could be assumed that cultural, mechanical and chemical treatments effective on the related E. angustifolia and E. umbellata would also be useful on E. pungens, especially those for E. umbellata as it occupies more similar climates and habitats. Control will need monitoring and repeated treatments to achieve success, and because seeds can be dispersed long distances by animals, it should also be eradicated in surrounding areas. Control can likely be achieved through eradication of individuals by hand pulling or spot applications of herbicide.
Hand-pulling of smaller plants would be effective, but as plants will resprout, mechanical or physical means that do not remove the roots are unlikely to be effective. Fire may also be appropriate (Munger, 2003).
Zheng et al. (2006) have identified a range of natural enemies of E. pungens from its native range in China, some of which may prove effective as biological control agents.
Several herbicides have been used alone or in combination to provide effective control of E. umbellata and which may also prove effective on E. pungens (see Sather and Eckardt, 2001; Munger, 2003). Dicamba, glyphosate or 2,4-D (but not metsulfuron methyl) have been used as effective foliar-applied herbicides especially on shorter plants. On larger plants, glyphosate, triclopyr and/or 2,4-D are used effectively on regrowth; also basal-bark applications of triclopyr. In an invaded tree plantation in Illinois, USA, triclopyr reduced E. umbellata from 12.5 to 3.9 stems/m2, but it is recommended that intensive control efforts focusing on relatively small areas in large well-established populations are only moderately effective and control efforts must be repeated every 5 years to achieve eradication (Edgin and Ebinger, 2001).